This invention relates to the manufacture of tubular articles such as hose, and more particularly to tubular articles comprising an inner core formed of vulcanizable elastomeric material, such as natural and synthetic rubbers.
In the manufacture of reinforced hose having a vulcanizable core tube, it is customary to twine the reinforcement in the form of a braid, spiral or the like about the uncured elastomer core. The reinforcement may be treated with an adhesive dip. A cover may be optionally extruded over the reinforced core tube, and then the green composite cured (vulcanized) in customary fashion employing, for instance, open steam or lead-press methods. For many applications the foregoing process is less than satisfactory since the uncured core will neckdown, stretch, flatten, or otherwise experience a diameter or shape change during braiding or other application of reinforcement. This results in an uneven braid pattern and angle and undesirable change in the shape of the core tube, and particularly a loss in roundness. The neckdown problem makes it more difficult to braid or spiral the reinforcement at the locking angle of 54.7 degrees.
To overcome the problem of shape change associated with the above-described method, normally one of two techniques has been employed. First, the core is fully cured prior to applying the reinforcement thereover. The severe drawback with this approach, however, is a loss of adhesion between the reinforcement and the cured core, so that the yarn becomes loose on the core and tends to fray out or flare at the cut end of the hose. The second solution has been to employ a flexible rubber supportive mandrel internally of the core during application of the reinforcement. While the above problems are primarily overcome when using the mandrel, there still tends to be a degree of neckdown of the core since its entire wall section is uncured, relatively soft, and lacking in resiliency. Moreover, the use of the mandrel adds considerable expense to the process.
It is the primary object of the subject invention to overcome the problems of the prior art, and to produce a core whose cross section and length are held virtually constant during twining of the reinforcement about the core, without sacrificing adhesion between the reinforcement and core.